Solution cast double base propellants and method

ABSTRACT

1. A method for the preparation of a double base propellant grain which comprises the steps of 1. PRETREATING NITROCELLULOSE BY A. STIRRING 100 GRAMS OF DRY NITROCELLULOSE INTO A SOLUTION OF 2 GRAMS OF PHENYL ISOCYANATE IN 500 GRAMS OF CARBON TETRACHLORIDE, B. FILTERING THE RESULTING MIXTURE AND C. DRYING THE RESIDUE; 2. ROTATIONALLY STIRRING 15 PARTS BY WEIGHT OF THE PRETREATED NITROCELLULOSE WITH 3 PARTS RED LEAD, 1 PART NITRODIPHENYLAMINE, 57.1 PARTS BY WEIGHT NITROGLYCERIN AND 23.6 PARTS BY WEIGHT TRIACETIN UNTIL A VISCOUS MIXTURE RESULTS, 3. ADDING TO THIS MIXTURE TOLYLENE DIISOCYANATE, 4. TRANSFERRING THE RESULTING MIXTURE UNDER REDUCED PRESSURE TO A CONTAINER AND, 5. CURING FOR 5 DAYS AT 50* C.

United States Patent Elrick Sept. 23, 1975 [54] SOLUTION CAST DOUBLE BASE 3,106,498 10/1963 Grable 149/96 PROPELLANTS AND METHOD P E s h J L h J rimury .taminertep en ec ert, r.

[75] Inventor Donald Elnck Rdwlmgs Attorney, Agent. or FirmR. S. Sciascia; Roy Miller [73] Assignee: The United States of America as represented by the Secretary of the EXEMPLARY CLAIM Navy, Washington, DC. 1. A method for the preparation of a double base pro- [22] Filed, Jan 30 1964 pellant grain which comprises the steps of [52] US. Cl. 149/2; 149/92; 149/95; 149/98; 264/3 R; 264/3 C [51] Int. Cl. C06B 45/00 [58] Field of Search 149/96, 97, 98, 99, 18, 149/19, 2, 95, 92; 264/3 R, 3 C

[56] References Cited UNITED STATES PATENTS 2,916,778 12/1959 O'Neill 149/96 2,967,098 l/l961 Well 149/19 3,002,830 10/1961 Barr 149/19 3,033,715 5/1962 Preckel 149/96 3,036,939 5/1962 Camp 149/19 pretreating nitrocellulose by a. stirring 100 grams of dry nitrocellulose into a solution of 2 grants of phenyl isocyanate in 500 grams of carbon tetrachloride,

b. filtering the resulting mixture and c. drying the residue;

. rotationally stirring 15 parts by weight of the pretreated nitrocellulose with 3 parts red lead. 1 part nitrodiphenylamine, 57.1 parts by weight nitroglycerin and 23.6 parts by weight triacetin until a viscous mixture results.

. adding to this mixture tolylene diisocyanate, transferring the resulting mixture under reduced pressure to a container and.

. curing for 5 days at 50 C.

9 Claims, N0 Drawings SOLUTION CAST DOUBLE BASE PROPELLANTS AND METHOD This invention relates to high performance solution cast double base propellant compositions and to the method of preparation.

Propellant systems containing nitrocellulose. nitroglycerin and other ingredients have been prepared in a number of ways. Cast propellants are generally prepared by first preparing-small, hard, high density easting powder particles containing colloided nitrocellulose and other additives and then casting and curing in a suitable container. Other cast propellants are prepared using a plastisol process in which very small particles containing colloided nitrocellulose are mixed with various additives and a casting solvent until a desired viscosity is attained in the mixture is then cast. Extruded propellantsrequire mixing of the necessary ingredients and extruding under high pressure with tremendous pressures being required for larger grains. The present invention relates generally to improvements in preparing propellant systems and more particularly to new and improved solution cast propellants which require no colloided nitrocellulose particles and only mixing and casting containers are needed.

The primary object of the present invention is a means of preparing high performance propellants which can be liquid loaded into a motor and by means of crosslinking converted to a solid grain bonded to the rocket motor.

Another object is the provision of an improved east ing system which offers the economic advantages of reduced time, equipment, and labor.

A further object is to provide a method whereby grains of intricate geometry can be readily cast.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same become better understood in the following detailed description.

This invention involves the preparation ofhigh performance propellants by dissolving lacquer grade nitrocellulose in nitroglycerin or in a casting solvent and crosslinking the nitrocellulose by use of a polyisocyanate to form upon curing a relatively tough gel. A lead salt, which serves as a crosslinking catalyst and a ballistic modifier, is incorporated into the solution. By varying the ballistic modifier and the heat of explosion of the matrix, compositions of varying burning rates can be prepared. These mixtures can be liquid loaded into rocket motors to produce case bonded propellants. The method involved herein is concerned with (l the solution of a lacquer grade nitrocellulose in an explosive solvent, (2) the use of any polyisocyanate as a crosslinking agent, (3) the ballistic modification of the composition by any modifier, which does not adversely affect the reaction of nitrocellulose with an isocyanate. If the ballistic modifier should not be a catalyst for the urethane erosslink formation, such a catalyst may be added to the composition. if the modifier should have an adverse effect upon urethane formation, the modifier may be coated to prevent this adverse effect and a crosslinking catalyst may be added to the composition.

Other crosslinking systems can be used, including titanates, epoxides, anydrides, etc. 7

A more comprehensive understanding of this invention is obtained by reference to the following example:

EXAMPLE l 10 parts dry (I 1.9%N) nitrocellulose 3 parts red lead 1 part ethyl Ccntralite 60.1 parts nitroglycerin 24.9 parts triacetin were rotationally stirred until nitrocellulose had been dissolved. To the viscous mixture was added 1.2 parts of tolylene diisocyanate and the mixture was transferred under pressure to a steel motor. This mixture, which weight 470 g. and had a heat of explosion of 804 cal./g., was allowed to cure for about 56 days at about 25C. to produce a case bonded propellantwith the appearance of a gel. The propellant was fired at a K of 1038 to obtain the following data:

Burning time 26.9 sec. Burning rate 0093 inJsce. Average pressure during burning 525 psi.

"EXAMPLE II The nitrocellulose used in this example was first pretreated. Dry nitrocellulose I00 grams) was stirred with a solution of 2 grams of phenylisocyanate in 500 grams of carbon tetrachloride. filtered, and dried. Then,

15 parts pretreated nitrocellulose 3 parts red lead 1 part 2-nitrodiphenylamine 57.1 parts nitroglycerin 23.6 parts triacetin were rotationally stirred until nitrocellulose had been dissolved to form a viscous mixture. To this mixture 0.4 parts of tolylene diisocyanate was added..The mixture was then transferred under reduced pressure to a steel motor coated internally with a 1 mil binder of partially crosslinked cellulose acetate. The mixture which weighed 950 grams and had a heat of explosion of 824 caL/gram, was allowed to cure for 5 days at 50C. to produce a case bonded propellant with the characteristics of a relatively tough gel. The propellant was fired at a K of 793 to obtain the following data:

58.4 sec.

Burning time Burning rate 0.086 in./sec.

Average pressure during burning 370 psi EXAMPLE ll] 15 parts pretreated nitrocellulose (see Example ll) 3 parts lead stearate 2 parts nitrodiphenylamine 56.8 parts nitroglycerin 22.7 parts triacetin were rotationally stirred until nitrocellulose was in solution forming a viscous mixture to which 0.6 parts of tolylene diisocyanate was added. The mixture was then transferred under reduced pressure to a steel motor, coated internally with 1 mil binder of partially crosslinked cellulose acetate. The mixture which weighed 925 grams and had a heat of explosion of 748 cal./g. was allowed to cure for 7 days at 50C. to produce a case bonded propellant with the characteristics ofa rel- Burning time 3a.: sec. Burning rate 0.131

in./scc. Average pressure during burning 740 psi.

EXAMPLE IV 20 parts by weight of casting powder consisting of 75% (11.9%N. 20 cp.) nitrocellulose 23% nitroglycerin 2% nitrodiphenylamine 3 parts dibasic lead phthalate 1.9 parts triacetin 75.1 parts castingsolvent containing 70% nitroglycerin 29% triacetin 1% nitrodiphenylamine were rotationally stirred until a viscous mixture formed. To this mixture 0.3 parts phenyl isocyanate were added and the mixture again rotationally stirred. Any unreacted isocyanate was removed under reduced pressure. Then 0.4 parts of tolylene diisoeyante was added to the mixture which was poured into a steel motor, coated internally with a 1 mil binder of partially crosslinked cellulose acetate. The mixture was allowed to cure for 3 days at about 50C. to produce a case bonded propellant with characteristics of a tough gel. The propellant was fired at a K of 903 to obtain a burning rate of 0.33 at a pressure of 2160 psi.

EXAMPLE V 22.2 parts by weight casting powder containing 70% (11.9%N. 20 cp.) nitrocellulose 13.6% nitroglycerin 14% dibasic lead phthalate 1.4% nitrodiphenylamine 77.8 parts of a casting solvent containing 75% nitroglycerin 24% triacetin 1% nitrodiphenylamine were rotationally stirred until the nitrocellulose was in solution forming a viscous mixture. After 0.3 parts of phenyl isocyanate had been added, the viscous mixture was rotationally stirred and excess isocyanate was removed under reduced pressure. Then 0.4 parts tolylene diisocyanate was added and the mixture transferred to a steel motor. coated internally with a 1 mil binder of partially crosslinked cellulose acetate. The mixture. which had a heat of explosion of 953 cal./g.. was allowed to cure for three days at 50C. to produce a case bonded propellant. A total of three motors were prepared in the above manner to obtain the following ballistic data: a rate of 0.39 in./sec. at 1000 psi with a slope of 0.20 from 5001000 psi. A cast dumbbell specimen gave the following data: at -20F. maximum stress 44 psi, modulus 49 psi and elongation greater than 91%; at 40F. maximum stress 67 psi, modulus 233 psi and elongation 93%.

EXAMPLE V1.

17.9 parts casting powder containing 70% (11.9%N, 20 cp.) nitrocellulose 13.6% nitroglycerin 14% dibasic lead phthalate 14% carbon black 1% nitrodiphenylamine 82.1 parts casting solvent containing 97% diglycol dinitrate 3% nitrodiphenylamine were rotationally stirred until the nitrocellulose was in solution forming a viscous mixture. After 0.3 parts phenyl isocyanate had been added. the viscous mixture was rotationally stirred at 35C. for two hours and ex cess isocyanate was removed under reduced pressure. To the mixture was added 0.4 parts of tolylene diisocyanate and the mixture was transferred at 35C. under reduced pressure to steel motors. coated internally with 1 mil crosslinked cellulose acetate binder. The mixture which had a heat of explosion of 865 cal./gram was allowed to cure for three days at C. to produce case bonded propellants having the characteristics of relatively tough gel. There was obtained at a K of 386 a burning rate of 0.48 in./sec. at 1365 psi. and at a K of 244 a burning rate of 0.44 in./sec. at 675 psi.

EXAMPLE V11 22.2 parts casting powder containing 70% nitrocellulose (11.9%N) 13.6% nitroglycerin 14% dibasic lead phthalate 1.4% carbon black 1% nitrodiphenylamine v 77.8 parts casting solvent containing 75% glycol dinitrate 24% triacetin 1% nitrodiphenylamine were rotationally stirred until the nitrocellulose was in solution. After 0.25 parts of phenyl isocyanate had been added. the viscous mixture was again rotationally stirred and excess isocyanate was removed under reduce pressure. To the mixture was added 0.4 parts of tolylene diisocyanate and the mixture was transferred under reduced pressure to a steel motor. coated internally with a binder of partially crosslinked cellulose acetate. The mixture which had a heat ofexplosion of 937 cal/gram was allowed to cure for three days at 50C. to produce a tough gel. The case bonded propellant was fired at a K of 396 to obtain a burning rate of 0.34 in./sec. at 865 psi.

EXAMPLE V111 22.2 parts casting powder containing 70% nitrocellulose (11.9%N)

22.9% nitroglycerin 4.7% tribasic'leacl maleate 1% nitrodiphenylamine 1.4% carbon black 77.8 parts casting solvent containing 75% nitroglycerin 24% triacetin 1% nitrodiphenylamine 989 cal/gram was allowed to cure at 50C. to produce a soft gel of a case bonded propellant. The propellant was fired to obtain the following ballistic data: a rate of 0.34 in./sec. at 1000 psi with a slope of 0.57 from 500 1 100 psi.

EXAMPLE IX A slurry containing 27.4 parts by weight of 95% ethanol and 72.6 parts by weight of mixture consisting of 90.8% (12.2%N, 20 cp.) nitrocellulose 6.1% tribasic lead maleate 1.3% nitrodiphenylamine 1.8% carbon black (Carbolac 1) was prepared and stirred for one hour in a Sigma Blade Mixer.

20.4 parts of the mixture 4.6 parts 95% ethanol 75.0 parts of a casting solvent containing 76.5% nitroglycerin 22.6% triacetin 0.9% nitrodiphenylamine were rotationally stirred until a slightly viscous mixture formed. The ethanol was removed under reduced pressure and 0.25 parts of phenyl isocyanate was added. This mixture was rotationally stirred for one hour and excess isocyanate was removed under reduced pressure. To this mixture was added a total of 1.4 parts tolylene diisocyanate and the mixture was transferred under reduced pressure to a steel motor coated internally with a binder of partially crosslinked cellulose acetate. The mixture which had a heat ofexplosion of 989 caL/gram was cured for three days at 50C. to produce a soft gel of case bonded propellant. The propellant was fired at a K of 178 to obtain a burning rate of 0.28 in./sec. at 650 psi.

EXAMPLE X To a mixture of 4.5 grams of nitrocellulose (11.9%N), 0.9 grams of dibasic lead phthalate, 0.06 grams of nitrodiphenylamine and 0.09 grams of carbon black (Carbolac l) in a large amount of methylene chloride was added with stirring a total of 27.6 grams of 99% nitroglycerin 1% ethyl Centralite and 0.08 grams of phenyl isocyanate. After methylene chloride and excess isocyanate were removed, 0.12 grams of tolylene diisocyanate was added and the mixture was placed in strand molds, cured for two days at 50C. and fired to obtain burning rates of 0.73 and 0.82 in./sec. at 810 and 1010 psi respectively.

EXAMPLE X1 A solution containing 20 parts dry nitrocellulose (l 1.9%N) and 80 parts dimethylsulfoxide was poured through a perforated plate and allowed to fall freely for 16 inches through air into water. The resulting pellets were extracted with water and dried to obtain porous nitrocellulose pellets with a loading density of 0.2 g./ml.

13.6 parts of these porous pellets 83.2 parts of a casting solvent containing 99% nitroglycerin 1% ethyl Centralite 2.7 parts dibasic lead phthalate 0.3 parts carbon black (Carbolac 1) 0.2 parts nitrodiphenylamine were mixed by rotational stirring and evacuation under reduced pressure until a viscous mixture resulted. About 0.25 parts phenyl isocyanate was then added and stirred. Excess isocyanate was removed under reduced pressure then 0.3 parts of tolylcnc diisocyanate was added and the mixture was cast in strand molds and in a steel rocket motor lined with partially crosslinked cellulose acetate. This propellant which had a heat of explosion of 1547 cal/gram was allowed to cure for three days at 50C. and produced a relatively tough gel. Strand burning rates gave a burning rate of 1.14 in./sec. at 1000 psi with a slope of 0.56. The case bonded propellant in the motor was fired at a K of 81 to obtain a rate of 0.75 in./sec. at 500 psi.

EXAMPLE X11 To a stirred mixture of 1 part dibasic lead phthalate 0.4 parts of'nitrodiphenylamine in 22.1 parts of triacetin at 40C.. 15 parts dry phenyl isocyanate pre-treated nitrocellulose was added with continuous stirring then 61.5 parts of a casting solvent containing 75% nitroglycerin 24% triacetin 1% nitrodiphenylamine was added and the mixture was rotationally stirred until a slightly viscous slurry was formed. To this mixture a total of 1.6 parts of tolylene diisocyanate was added and the mixture transferred under reduced pressure to a steel rocket motor which had been coated with a partially crosslinked cellulose acetate. The mixture which had a heat of explosion of 412 cal./g., was allowed to cure for three days at 50C. to produce a case bonded propellant with the characteristics of a slightly soft gel.

As described in the examples herein set out. this invention is concerned with the manufacture of high performancce solution cast propellants which are prepared by first dissolving a lacquer grade nitrocellulose in nitroglycerin or casting solvent with the simulta neous solution or suspension of additives and then after addition of a polyisocyanate, pouring the mixture intc a motor and curing.

Dissolution of the nitrocellulose is accomplished in number of ways. Powder dry nitrocellulose which has been adequately wetted with casting solvent gradually dissolves to form a clear solution. Thorough wetting o: nitrocellulose fibers is not easily accomplished in this manner; agglomerates of partially gelled nitrocellulose tend to form and may require long times to CllSSOlVt completely (Examples 1. 11 and 111). Quicker solutior was obtained by slurrying the nitrocellulose in cold tri acetin and then adding the casting solvent. Dissolutior of nitrocellulose is essentially negligible in the cold sol vent and no agglomerates normally form. The dis persed nitrocellulose then dissolves rapidly WllCl heated with stirring (Example X11). Other methods 0 obtaining the slurrying state involve the use of non solvents. Nitrocellulose can be slurried in ethanol 0 methylene chloride and casting solvent added. Th1 slurrying state is maintained as nitrocellulose is gradu ally dissolved during removal of the non-solvent. Etha nol is, however, not entirely satisfactory as lacque grade nitrocellulose is slightly soluble therein (Exampl IX). Methylene chloride is an excellent slurrying medium and dissolution occurs rapidly. Methylene chloride wet nitrocellulose could satisfy the requirements of desensitized nitrocellulose (Example X). Other slurrying media such as diethyl ether or chloroform should also be satisfactory. Much of the work has been done using a casting powder as the source of the nitrocellulose (Example lV to Vlll). Optimum ballistic performance for a composition is obtained only if the modifiers are well dispersed. Casting powder was used herein a source of the nitrocellulose to insure satisfactory modifier dispersion and optimum ballistic performance. Ballistic modifiers may also be dispersed in water wet nitrocellulose by subjecting such a mixture to the action of a sigma blade mixer. lnc orporation of the modifiers in all solution cast propellants may be easily accomplished by premixing modifier and nitrocellulose. Another method for obtaining nitrocellulose solutions involves the use of porous nitrocellulose pellets. The casting solvent would rapidly wet the porous pellets allowing dissolution to occur rapidly. Good means of stirring would be required since the casting solvent wet'powder tends to coalesce (Example Xl).

Compositions containing this lacquer grade nitrocellulose had a tendency to gas upon curing an at elevated temperature (50C.). Gassing did not occur upon curing at 25C. (Example I). Gassing at elevated temperatures was eliminated by either treating anhydrous nitrocellulose with a dilute solution of phenyl isocyanate in carbon tetrachloride (Examples ll. lll, X") or by adding phenyl isocyanate to the nitrocellulose casting solvent solution prior to final casting (Examples 1V XI).

The reason for gassing is not known, though carbon dioxide can be formed when an isocyanate reacts with water or an acid. It appears that the gas formation with untreated nitrocellulose may be traceable to residual sulfate or the relatively high carboxyl content of the 7 have to be added to the mixture in solution with a portion of the casting solvent. Other polyisocyanates such .as polyaryl polyisocyanate or 3.3 dimethyl diphenylmethane 4,4 diisocyanate could also be substituted for tolylene diisocyanate. Other crosslinking systems can be used. including titanates, epoxides, anhydrides. etc.

The lead salt has a dual function of ballistic modifier and crosslinking catalyst. Red lead (Pb-,0.) has been used as a crosslinking catalyst (Examples l and ll), since its catalysis of the nitrocellulose-isocyanate reaction would give the desired rate of crosslinking. About 60% of the isocyanate reacted in 20 hours and 80% in 40 hours at C. The mixture-containing the polyisocyanate must have sufficient pot life for a casting period of about three hours. Lead stcarate was also a satisfactory catalyst (Example Ill) in that eight hours were required to react of the isocyanate at 55 C. Dibasic lead phthalate (Examples 1V to VII; X to X11) and tribasic lead maleate (Examples Vlll and IX) have catalytic effects similar to red lead although no rates have been determined. Compositions containing 3% red lead or lead stearate and having a heat of explosion of 750 825 caL/g. gave burning rate slopes of about 1 (Examples l to lll). When the ballistic modifiers were 1% tribasic lead maleate and 0.3% carbon black and the heat of explosion of 989 eal./g. a

Other nitrocellulose of varying viscosity and nitrogen content have been incorporated in solution cast propellants and evaluated. The mixture that is poured into a rocket motor must be sufficiently viscous to prevent settling of solids such as ballistic modifiers and yet must be sufficiently fluid for pouring purposes. The strength of the resulting gel is dependent on the amount of nitrocellulose in the mixture. Thus the nitrocellulose that is best suited for solution cast propellants is the one processable at the highest attainable concentration in the mixture. The maximum workable concentration of var ious nitrocellulosoe in solution cast propellants is as follows: for 12.6%N, 10 to [8 sec., millitary grade -2.8% for 12.2%N, 5 to 6 sec. -6.0%; for 11.0%, [.4 sec. -7% and for l 1.9 to 12.2%N, 20 cp. -l5%. burning rate of 0.34 in./sec. at 1000 psi. and a slope of 0.57 was obtained (Example Vlll). When 3% dibasic lead phthalate and 0.3% carbon black were the ballistic modifiers and the heat of explosion was 953 cal./g., a rate of 0.39 in./sec. at 1000 psi with a slope of 0.20 from 500 1000 psi was obtained (Example V). When 3% dibasic lead phthalate and 0.3% carbon black were the ballistic modifiers and the heat of explosion was 1547 cal./g., a rate of 1.14 in./sec. at 1000 psi with a slope of 0.56 from 500 l psi was obtained (Example XI).

Explosive plasticizers other than nitroglycerin have been incorporated into these propellants. When glycol dinitrate replaced most of the nitroglycerin in a composition containing 3% dibasic lead phthalate and 0.3% carbon black and having a heat of explosion of 937 cal./g., a burning rate of 0.34 in./sec. at 856 psi was obtained (Example Vll). When diglycol dinitrate was used in a similar composition which had a heat of explosion of 865 cal./g., an interpolated burning rate of 0.46 in./sec. at 1000 psi was obtained (Example Vl).

Other nitrocelluloses of varying viscosity and nitrogen content have been incorporated into solution cast propellants and evaluated. The mixture that is poured into a rocket motor must be sufficiently viscous to prevent settling of solids such ballistic modifiers and yet must be sufficiently fluid for pouring purposes. The strength of the resulting gel is dependent on the amount of nitrocellulose in the mixture. Thus the nitrocellulose that is best suited for solution cast propellants is the one processable at the highest attainable concentration in the mixture. The maximum workable concentration of various nitrocelluloses in solution cast propellants is as follows: for 12.6%N. 10 to 18 sec.. military grade 2.8%; for l2.2%N, 5 to 6 sec. 6.0%; for 11.0%, 1.4 sec. 7% and for ll.9 to l2.2%N. 20 cp. 15%.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

l. A method for the preparation ofa double base propellant grain which comprises the steps of l. pretreating nitrocellulose by a. stirring 100 grams of dry nitrocellulose into a solution of 2 grams of phenyl isocyanate in 500 grams of carbon tetrachloride.

h. filtering the resulting mixture and c. drying the residue; i

2. rotationally stirring parts by weight of the pretreated nitrocellulose with 3 parts red lead. 1 part nitrodiphenylamine. 571 parts by weightnitroglycerin and 23.6 parts by weight triacetin until a viscous mixture results. i v

3. adding to this mixture tolylene diisocyanate,

4. transferring the resulting mixture under reduced pressure to a container and,

5. curing for 5 days at 50C.

2. A method for the preparation ofa double base propellant grain which comprises the steps of l. stirring 22.2 parts by weight of a casting powder consisting of a. 70% nitrocellulose b. 13.6% nitroglycerin c. 14% dibasic lead phthalate d. 1.4% carbon black e. 1% nitrodiphenylamine with 77.8 parts by weight of a casting solvent consisting of a. 75% nitroglycerin b. 24% triacetin c. 17: nitrodiphenylaminc until a viscous mixture results,

2. adding while stirring 0.3 parts by weight phenyl isocyanate,

3. removing excess phenyl isocyanate under reduced pessure,

4. adding 0.4 parts by weight tolylene diisocyanate,

5. transferring the resulting mixture to a container and 6. curing for three days at 50C.;

all percentages being by weight.

3. A method for the preparation ofa propellant grain which comprises the steps of 1. providing porous nitrocellulose pellets prepared by a. mixing 20 parts by weight dry nitrocellulose with 80 parts by weight dimethylsulfoxide to form a solution,

b. pouring said solution through a perforated plate through air into water to form pellets,

c. extracting said pellets with water and d. drying to obtain porous nitrocellulose pellets;

2. stirring 13.6 parts by weight of said pellets with 83.2 parts by weight of a casting solvent consisting of a. 99% nitroglycerin and b. 1% ethyl Centralite 2.7 parts by weight dibasic lead phthalate 0.3 parts by weight carbon black 0.2 parts by weight nitrodiphenylamine until a viscous mixture results, while stirring 3. adding while stirring 0.25 parts phenyl isocyanate,

4. removing under reduced pressure excess isocyanate 5. adding 0.3 parts tolylene diisocyanate,

6. pouring the resulting mixture into a rocket motor.

and

7. curing for three days at 50C.

4. A propellant composition consisting essentially of Tolylcne-diisocyanate 5. A propellant composition consisting essentially of Ingredients Parts by weight Nitrocellulose degassed in a solution of phenyl isocyanate and carbon tetrachloride Rcd lead 3 Nitrodiphenylaminc l Nitroglycerin 57.0 Triacetin 23.6 Tolylene diisocyanate 0.4.

6. A propellant composition consisting essentially of Ingredients Parts by weight Nitrocellulose pellets Casting solvent consisting of 9971 nitroglycerin and 1V:

ethyl Centralite Dihasic lead phthalatc Carbon black Nitrodiphenylamine Tolylene diisocyanate 7. A propellant composition consisting essentially of Ingredients Parts by weight Casting powder consisting of 20 75'?! nitrocellulose. 2371 nitroglycerin and 27: nitrodiphenylamine Dibasic lead phthalate Triacetin Casting solvent consisting of 7 7: nitroglycerin. 297: triacetin and 17! nitrodiphenylamine Tolylenc diisocyanate 8. A propellant composition consisting essentially of lngredients Parts by weight Casting powder consisting of 17.9

70% nitrocellulose. 13.6% nitroglycerin. [4'71 dihasic lead phthalate.

1.4% carbon black and 17: nitrodiphenylamine Casting solvent consisting of 97% diglycol dinitratc and 371 nitrodiphcnylamine Tolylene diisocyanate 9. A method for the preparation ofa double base propellant grain which comprises the steps of 1. pretreating nitrocellulose by a. wctting dry nitrocellulose with methylene chlomixture in a solution of methylene chloride and a d casting solvent consisting essentially of an explob. mixing the wet nitrocellulose into a solution of i plasticizcn u n )n c (plogivc l i i d a phenyl isocyanate and methylene ChlOl'ldC. Stabilizer um a slurry is fOrmcCL c. filtering the mixture to obtain the nitrocellulose.

d drying the nitrocellulose, I

e. adding water to the nitrocellulose in an amount of about 30 parts water to 70 parts nitrocellulose f. stirring a ballistic modifier with the water wetted addmg wlylcnc dnsocyanate m the slurry nitrocellulose to form a mixture in which the S. transferring the slurry under reduced pressure to modifier is well dispersed. a comalncrand l g. drying the mixture; 6. curing for from 4 to 7 days at about 50C.

2. stirring the pretreated nitrocellulose and modifier 5 3. removing methylene chloride from the slurry as stirring continues and as nitrocellulose goes into solution. 

1. A METHOD FOR THE PREPARATION OF A DOUBLE BASE PROPELLANT GRAIN WHICH COMPRISES THE STEPS OF
 1. PRETREATING NITROCELLULOSE BY A. STIRRING 100 GRAMS OF DRY NITROCELLULOSE INTO A SOLUTION OF 2 GRAMS OF PHENYL ISOCYANATE IN 500 GRAMS OF CARBON TETRACHLORIDE, B. FILTERING THE RESULTING MIXTURE AND C. DRYING THE RESIDUE,
 2. ROTATIONALLY STIRRING 15 PARTS BY WEIGHT OF THE PRETREATED NITROCELLULOSE WITH 3 PARTS RED LEAD, 1 PART NITRODIPHENYLAMINE, 57.1 PARTS BY WEIGHT NITROGLYCERIN AND 23.6 PARTS BY WEIGHT TRIACETIN UNTIL A VISCOUS MIXTURE RESULTS,
 2. stirring the pretreated nitrocellulose and modifier mixture in a solution of methylene chloride and a casting solvent consisting essentially of an explosive plasticizer, a non-explosive plasticizer and a stabilizer until a slurry is formed,
 2. rotationally stirring 15 parts by weight of the pretreated nitrocellulose with 3 parts red lead, 1 part nitrodiphenylamine, 57.1 parts by weight nitroglycerin and 23.6 parts by weight triacetin until a viscous mixture results,
 2. A method for the preparation of a double base propellant grain which comprises the steps of
 2. adding while stirring 0.3 parts by weight phenyl isocyanate,
 2. stirring 13.6 parts by weight of said pellets with 83.2 parts by weight of a casting solvent consisting of a. 99% nitroglycerin and b. 1% ethyl Centralite 2.7 parts by weight dibasic lead phthalate 0.3 parts by weight carbon black 0.2 parts by weight nitrodiphenylamine until a viscous mixture results, while stirring
 3. removing excess phenyl isocyanate under reduced pessure,
 3. A method for the preparation of a propellant grain which comprises the steps of
 3. adding while stirring 0.25 parts phenyl isocyanate,
 3. adding to this mixture tolylene diisocyanate,
 3. removing methylene chloride from the slurry as stirring continues and as nitrocellulose goes into solution,
 3. ADDING TO THIS MIXTURE TOLYLENE DIISOCYANATE,
 4. TRANSFERRING THE RESULTING MIXTURE UNDER REDUCE PRESSURE TO A CONTAINER AND,
 4. adding tolylene diisocyanate to the slurry,
 4. transferring the resulting mixture under reduced pressure to a container and,
 4. removing under reduced pressure excess isocyanate
 4. A propellant composition consisting essentially of
 4. adding 0.4 parts by weight tolylene diisocyanate,
 5. transferring the resulting mixture to a container and
 5. A propellant composition consisting essentially of
 5. adding 0.3 parts tolylene diisocyanate,
 5. curing for 5 days at 50*C.
 5. transferring the slurry under reduced pressure to a container, and
 5. CURING FOR 5 DAYS AT 50*C.
 6. curing for from 4 to 7 days at about 50*C.
 6. pouring the resulting mixture into a rocket motor, and
 6. A propellant composition consisting essentially of
 6. curing for three days at 50*C.; all percentages being by weight.
 7. A propellant composition consisting essentially of
 7. curing for three days at 50*C.
 8. A propellant composition consisting essentially of
 9. A method for the preparation of a double base propellant grain which comprises the steps of 